Mineral Profile 2 Copper Formed Fromcopperleachednear-Surface Sulphides

Copper June 2007

This commodity profile provides an overview of

nt Symbol Cu copper, with up-to-data information on world

opme production, trade and prices. Emphasis is placed Atomic number 29 vel on the British perspective. It is one of a series on de l

ra important mineral commodities intended to inform a Atomic weight 63.546 UK

ne non-specialist audience.

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e Available from www.mineralsuk.com. Density at 293 K 8960 kg/m bl na

ai Melting point 1083 ºC st

su Definition, mineralogy and r Boiling point 2567 ºC f o deposits re

nt Specific heat 386 J/kg Ce Minerals Definition and characteristics capacity at 293 K Copper is a non-ferrous base metal and its average % (International concentration in the earth’s crust is about 50 ppm (parts Electrical 100 Annealed Copper per million). The average minimum exploitable grade for a conductivity Standard) copper deposit is 0.4% which equates to a concentration factor of around 80 based on average crustal abundance. Electrical Copper occurs naturally in all plants and animals, as it is conductivity at 5.98x107 Ohm-1m-1 an essential element for all known living organisms. 298 K

Electrical It is one of the 1.673 x 10-8 Ohm m transition metals in resistivity the periodic table which means it can Table 1 Properties of copper. form compounds, such as chalcopyrite the main copper

ore (CuFeS2), and copper ions (Cu+ or Cu2+) in solution. © Getty Images Copper metal has a characteristic reddish

BGS © NERC brown colour, with a metallic lustre Figure 1 Native copper. on fresh surfaces. However, it quickly oxidises in air, a feature of all base-metals. Copper is relatively soft (2.5–3.0 on Moh’s scale of hardness). Other physical properties are summarised in Table 1.

Unless otherwise stated, copyright of materials contained in this report are vested in NERC. BGS © NERC 2007. All rights reserved. Mineral profile 2 Copper formed fromcopperleachednear-surface sulphides. secondary sulphides,suchaschalcociteandcovellite, malachite, chrysocollaandcovellite.Thethirdgroupare from weatheringofcoppersulphides,thatincludecuprite, A secondgrouparethecopperoxides,typicallyformed enargite. drothermal groups. Primaryorhypogene only asmallnumberoftheseareeconomicimportance than 150coppermineralshavebeenidentified,although Copper combineswithanumberofelementsandmore Mineralogy 4 3 2 1 deposits. Table 2 copper isderivedfromsulphidedeposits.Ofthe copper production.Estimatessuggestatleast90%of Disseminated coppersulphidedepositsdominateglobal (Table 2). Coppermineralscanbedividedintothree Supergene: describes mineralsformedwithintheEarthfrom descendingfluids,suchaspercolatingrainwater causingleaching. Magmatic: relatedto magma,moltenrockandfluidoriginating deepwithinorbelowtheEarth’s crust. Hydrothermal: hotfluids. Hypogene: describesmineralsformedwithin theearthbyascendingfluids. Chalcopyrite Chrysocolla Enargite Antlerite Azurite Malachite Bornite Covellite Cuprite Chalcocite Native copper Mineral name Common coppermineralsfoundineconomic 2 processesincludebornite,chalcopyriteand CuFeS CuSiO Cu Cu 2CuCO Cu Cu CuS Cu Cu Cu 3 3 2 5 2 2 Chemical AsS SO CO FeS O S formula 3 4 3 2 3 .2H (OH) (OH) 4 1 4 .Cu(OH) mineralsrelatedtohy 2 O 4 2 2 Max. Cucontent (wt%) 34.6 36.2 49.0 53.7 55.3 57.5 63.3 66.4 88.8 79.9 100.0 -

Figure 2 economic importance. in variableamounts,however, theseareoflimited Numerous othertypesofmineraldepositscontaincopper and supergene most significantonaglobalscale,althoughmagmatic geological environments.Hydrothermaldepositsare Copper depositsarefoundworldwideinavarietyof Deposits (Figure 2). accounting forapproximatelyhalfofallcopperproduction minerals, chalcopyriteisbyfarthemostimportant Chalcopyrite, theprimaryoreofcopper. 4 depositsarelocallyimportant(Table 3). www.mineralsuk.com 3

BGS © NERC 3 Copper Table 3 14 13 mineralssuchasquartz orfeldspar. 12 11 10 9 8 7 6 5 Copper skarns Stratabound: anoredepositthatisconfined toasinglesedimentarybedorhorizon. Intrusion: abodyofigneousrockemplaced intopre-existingrocks. Disseminated: small,fine-grainedparticles oforemineraldispersedthrougharock. Stockwork: networkofmanycross-cuttingveins. Sedimentary: rocksformedfrommaterial derivedfromotherrocksbyweathering. Red-bed Sediment-hosted Porphyry Deposit type Supergene Vein-style deposits Epithermal (SEDEX) Sedimentary exhalative deposits Magmatic sulphide sulphide (VMS) Volcanogenic massive Breccia: a rock thathasbeenmechanically, hydraulicallyor pneumaticallybroken intoangularfragments. Sedimentary basin:ageologically depressedarea containing sedimentary rocks. Ultramafic: darkcoloured rockscontainingalmostentirelyiron andmagnesium-bearingminerals virtuallynofelsic Mafic: darkcolouredrockscontainingiron- andmagnesium-bearingmineralse.g.olivine. Volcanic: relatingtovolcanoes. Summary ofmaincopperdeposittypes. Polymetallic veins copper deposits Contact metasomatic deposits hosted massivesulphide volcano-sedimentary- Volcanic-associated, mantos hosted copper, copper basaltic copper, volcanic- continental red-bed, Sandstone-hosted, Central Africantype Kupferschiefer-type, stratiform copper, Shale-hosted copper, Synonyms sulphides depositedfrom Bodies ofpolymetallic magmatic rocks of mafic associated withavariety Sulphide concentrations sedimentary sequences by submarinevolcano- Mineralisation hosted volcanic in sedimentary(s)and occurring inoxidisedzones Copper mineralisation rocks range ofsedimentary minerals occurringina disseminations ofcopper Stratabound related tointrusions disseminated grade stockwork Large, relativelylow- Description mineralisation enrichment ofprimary In-situ naturalsecondary of sources metres widefromavariety centimetres uptotensof fractures varyingfrom often developedalong Mineralised structures into carbonaterocks associated withintrusions by chemicalalteration Mineralisation formed systems temperature hydrothermal volcanic-related low- high-level ornearsurface breccias Veins, stockworksand volcanic source basins into sedimentary hydrothermal fluidsvented 13 withnoobvious 11 10 14 andultramafic (v)rocks associatedwith 8

6 deposits

5 to 7 9

Australia; RedDog,Alaska Broken HillandMcArthurRiver, Australia Noril’sk-Talnakh, Russia;Kambalda, Sudbury andVoisey’s Bay, Canada; Rio Tinto, Spain Bathurst andKiddCreek,Canada; Mantos Blancos(v),Chile Dzhezkazgan (s),Kazakhstan; Pine, USA Nchanga, Zambia;Lubin,Poland;White Indonesia Bingham Canyon,USA;Grasberg, Chuquicamata andLaEscondida,Chile; Examples Sarcheshmeh, Iran Erdenet, Mongolia; La Escondida, Chile; Butte, USA El Indio,Chile;CopperHills,Australia; Canyon, USA;Rosita,Nicaragua Ok Tedi, PapuaNewGuinea;Copper Monywa, Burma El Indio,Chile;Lepanto,Philippines;

www.mineralsuk.com Major deposit classes 2600 million tonnes with >2.0% Cu and 30–80 g/t Ag. Porphyry deposits The Central African Copperbelt is the world’s largest Porphyry copper deposits are currently the world’s province containing stratiform21 sediment-hosted copper main source of copper (50–60% of world production), mineralisation. The Copperbelt is a 600 kilometre long and molybdenum (99% of world production) and rhenium15. 50 kilometre wide belt extending across Zambia and the They are also significant sources of gold, silver and tin Democratic Republic of Congo. and a range of by-product metals. Porphyry deposits are associated with subduction16-related felsic17 igneous18 Boundaries between different base-metal deposit types in intrusions. As a result they occur in plate boundary sedimentary/volcanic sequences are sometimes unclear collision areas such as the Canadian Cordillera, the Andes and depend heavily on the selection criteria employed. Mountains and around the western margin of the Pacific Basin in the Philippines, Indonesia and Papua New Guinea. Red-bed copper deposits The two types of red-bed mineralisation are volcanic The mineralisation is fracture-controlled, typically and sedimentary. Volcanic-hosted deposits occur in consisting of stockwork of quartz veins and breccias mafic terrestrial lava flows and associated volcaniclastic containing copper sulphides with gold and/or molybdenum. sedimentary rocks with sulphides disseminated through Mineralisation can develop in both the intrusive and host permeable22 host rocks or filling cavities. rock, typically associated with a core of intense alteration passing outwards into distinct zones characterised by Sedimentary-hosted deposits form in red continental other secondary alteration19 minerals. Mineralisation may sediments deposited in oxidising environments and consist occupy several cubic kilometres and deposits typically of disseminated sulphide deposited in permeable layers contain hundreds of millions of tonnes of ore, although in the host rock. It is suggested that copper is precipitated they can range in size from tens of millions to billions of in these deposits when oxygen-rich fluids rise through tonnes. Copper grades generally range from 0.2 per cent to permeable zones and encounter reduced material such as more than 1 per cent. organic matter and pyrite.

Sediment-hosted deposits Sedimentary-hosted deposits are generally uneconomic Sediment-hosted deposits are the world’s second most due to their small size, although they have been worked important source of copper accounting for approximately at Dzhezkazaga, Kazakhstan and Paoli, USA. In contrast, 20% of world production. They are also important volcanic-hosted deposits are important copper producers. sources of lead, zinc and silver and the world’s primary Tonnages range from hundreds of thousands to hundreds source of cobalt, especially from the Central African of millions of tonnes, typically grading around one to four Copperbelt. Deposits consist of disseminations of fine- percent copper. grained sulphides in a variety of continental sedimentary rocks including black shale, sandstone and limestone. Volcanogenic massive sulphide (VMS) deposits These sequences are typically associated with red-bed VMS deposits are important sources of copper and many sandstones and evaporites20. other metals owing to their widespread distribution, substantial tonnages (0.1–500 million tonnes) and Tonnages vary, with the average being 22 million tonnes relatively high grades. Precious metals, including silver grading 2.1% Cu and 23 g/t Ag (Mosier et al 1986) but and gold, are common by-products. Ore bodies are large, can be as much as several hundred million tonnes. The stratiform lenses and sheets formed on the seafloor enormous Lubin orebody in south-west Poland contains through the discharge of metal-rich hydrothermal fluids.

15Rhenium: a rare, heavy, silvery-white metal used in alloys. 16Subduction: the movement of oceanic crust under continental or oceanic crust. 17Felsic: rock containing light coloured silicate minerals e.g. quartz and feldspar. 18Igneous: rocks which have a crystalline texture and appear to have consolidated from molten rock. 19Alteration: changes in the chemical or mineral composition of a rock. 20Evaporite: a sedimentary rock composed of minerals produced by evaporation of water e.g. gypsum and rock salt. 21Stratiform: an ore deposit that occurs as a specific sedimentary bed.

Copper Permeable: allows a gas or fluid to move through it.

4 www.mineralsuk.com They are formed in extensional tectonic23 settings with are deposits formed by the exhalation of brines29 into modern-day examples currently developing at spreading seawater or the seafloor sediments, causing chemical centres24 and in oceanic arc25 terranes. A mound-shaped, precipitation of minerals as the brine cools. stratabound massive sulphide body is typically underlain by a stockwork feeder zone. Deposits are generally SEDEX deposits display many similarities to VMS deposits, restricted to specific stratigraphic26 intervals within a except for the lack of close volcanic association. Deposits province and tend to occur in clusters. are typically represented by sheet or tabular lenses consisting of bands of fine-grained sulphide intercalated VMS deposits may be divided into three main categories with shale, silt and carbonate host rocks. The sulphide based on their mineralogy — Kuroko, Besshi and Cyprus bodies generally only measure a few metres thick but may types. Deposits vary in size considerably but are generally extend laterally for more than a kilometre. The median high grade and low tonnage, with some giants such as Rio tonnage for global deposits is 15 million tonnes with grades Tinto, Spain with around 250 million tonnes at 1% Cu, 2% of 5.6% Zn, 2.8% Pb and 30 g/t Ag (Briskey, 1986). Deposits Zn and 1% Pb (Galley et al.). may contain up to 1% copper. Broken Hill, McArthur River and Mount Isa in Australia, Meggen and Rammelsberg Magmatic sulphide deposits in Germany and Tynagh in Ireland are all SEDEX deposits A diverse group of deposits containing copper in containing copper. association with nickel and platinum-group elements (PGE) occurring as sulphide concentrations within mafic and Epithermal deposits ultramafic rocks. Epithermal deposits are important for their gold production but may contain significant quantities of silver, copper and As a magma27 rises through the crust it cools and, if the other metals. Deposits are associated with subduction- sulphur content of the magma is sufficient, a separate related environments at plate boundaries. These deposits liquid sulphide phase may develop (droplets of sulphide may take the form of veins, stockworks or breccias and are liquid in a silicate liquid). Elements such as nickel, copper, mainly Tertiary (63–2 million years) to Quaternary (2 million PGE and iron preferentially transfer into the sulphide phase years to present) in age. They usually form at shallow crustal from the surrounding magma. The metal-rich sulphide levels (300–600 m) by circulation of magmatic fluids through liquid tends to sink because of its greater density, forming volcanic rocks. Deposits are often spatially related to sulphide concentrations on the magma chamber28 floor. porphyry deposits. Principal ore minerals include chalcocite, covellite, bornite and native gold with minor amounts of Worldwide deposits typically grade between 0.2 and chalcopyrite. There is considerable variation in grade and 2% Cu with ore tonnages ranging from a few hundred tonnage of these deposits but they can be extremely rich thousand to tens of millions of tonnes. The largest e.g. El Indio, Chile with grades up to 178 g/t Au, 109 g/t Ag magmatic sulphide nickel-copper deposits are of Archean and 3.87% Cu (Panteleyev, 1996). (4000–2500 million years) and Proterozoic (2500–540 million years) age and are found at Sudbury, Ontario and Skarn deposits Noril’sk-Talnakh, Russia. A skarn is a metamorphic30 rock that forms as a result of chemical alteration by hydrothermal and other fluids. Sedimentary exhalative deposits (SEDEX) Copper skarns most frequently develop where granite31 These deposits are important sources of lead, zinc and intrusions are emplaced into continental margin32 silver. Copper may be a significant by-product in some carbonate sequences, such as limestone or dolomite, deposits. SEDEX, an acronym for ‘sedimentary exhalative’, causing intense alteration and mineral replacement.

23Extensional tectonics: the tectonic processes associated with the stretching of the Earth’s crust. 24Spreading centres: a region where two plates are being pulled apart and new crust is formed as molten rock is forced upward into the space e.g. Mid-Atlantic Ridge. 25Oceanic arc: a chain of volcanic islands produced as one plate moves under another and melts. 26Stratigraphic: the spatial ordering of geological layers or strata. 27Magma: molten rock. 28Magma chamber: a space below ground filled with magma. 29Brine: water saturated or close to saturation with salt. 30Metamorphic: rocks changed by temperature and pressure within the Earth’s crust. 31Granite: an intrusive rock dominated by quartz and feldspar. 32

Copper Continental margin: the zone of transition from a continent to ocean basin.

5 www.mineralsuk.com Deposits are highly variable in form ranging from takes place above the primary hypogene ore and can be tabular lenses to vertical pipes with irregular ore33 zones laterally and vertically extensive (reaching tens of metres controlled by the intrusive contact34. The largest copper downwards). This is an important process as it can affect skarns are associated with porphyry copper deposits. the economics of mining, especially of low-grade porphyry Copper mineralisation is present as stockwork veining and and VMS deposits. disseminations in both the intrusive and the surrounding host rock. Chalcopyrite tends to be the dominant copper Enrichment blankets containing high-grade copper mineral, occurring with bornite and tennanite35. Globally, minerals, such as chalcocite, covellite and bornite, may copper skarns average 1%–2% per cent copper, generally enhance the average grade of the ore to one to three ranging from one to hundred million tonnes, although some percent copper. Supergene enrichment favours rocks that exceptional deposits exceed 300 million tonnes. Major are permeable to meteoric water and contain abundant copper skarn mineralisation is associated with the Ok Tedi pyrite to allow the formation of oxidising acids. The porphyry intrusive system in Papua New Guinea. presence of acid-soluble metal-bearing minerals and a redox barrier40 (such as the water table) at depth may also Vein deposits contribute to the formation of supergene deposits. Vein deposits are intimately associated with many of the deposit classes discussed above. Veins are mineralised Supergene enrichment has been a major factor in the structures typically developed along fractures and varying development of several porphyry copper deposits. At La in thickness from centimetres to tens of metres or more. Escondida, in Chile, the supergene blanket constitutes Sulphides are commonly irregularly distributed as patches around 65% of the copper resource of the deposit. Grades and disseminations within quartz, carbonate and other of up to 3.5% Cu are recorded in this zone. A leached gangue36 minerals. cap containing lower grades of copper and molybdenum overlies the enriched sulphides. The importance of vein deposits has steadily diminished as changing economics and improved extraction Deposit styles – implications for exploitation techniques have allowed large, low-grade deposits to be The large size of porphyry copper deposits, their relatively mined. Copper commonly occurs in veins associated with low-grade and the intimate association of fractured host quartz, silver, gold and occasionally uranium, antimony rock, alteration and mineralisation makes them amenable and phosphorus. These polymetallic37 veins may be to opencast mining methods. With relatively thin horizons related to porphyry copper, copper skarn, epithermal such as those found in sediment-hosted copper deposits, gold-silver-copper and sediment-hosted copper deposits. higher grades are required as they are typically mined At the El Indio mine in Chile massive sulphide veins using underground methods. VMS deposits are sometimes can be over 10 m thick with average grades of 2.4% Cu viewed as less favourable targets for mining companies (Evans, 1993). when compared to porphyry and sediment-hosted copper deposits as a result of their complex mineralogy and Supergene deposits shape. However, due to their polymetallic nature, VMS Secondary enrichment can affect most classes of mineral deposits are advantageous during periods of fluctuating deposit. Supergene38 alteration is in-situ secondary metal prices. The shallow depth of formation of epithermal enrichment of a deposit whereby the primary ore minerals deposits generally allows the use of bulk open pit mining are oxidised, dissolved and reprecipitated by reduction, methods, although some higher grade deposits are commonly at the water table39. Supergene enrichment selectively worked underground.

33Ore: rock from which metal or minerals can be economically extracted. 34Intrusive contact: the zone between an intrusion and the surrounding host rock. 35Tennantite: a copper-iron-arsenic sulphide mineral. 36Gangue: the undesirable or unwanted minerals in an ore deposit. 37Polymetallic: comprised of a combination of metals. 38Supergene: ore minerals formed by processes commonly involving water containing dissolved material descending from the surface. 39Water table: underground surface below which the ground is completely saturated. 40Redox barrier: the zone at which oxidation-reduction reactions occur. Copper

6 www.mineralsuk.com Extraction methods and through the deposit. This copper-rich solution is pumped out through recovery wells which surround the injection processing well and prevent the leaching solution from escaping. On completion, fresh water is pumped around the system Extraction for cleaning and the wells are cemented. In the Mopani Copper ore is extracted using three principal techniques. mines on the Zambian Copperbelt, in-situ leaching is being The technique applied depends on the characteristics and conducted from old underground workings. geographic location of the ore body (Figure 3). Processing Open-pit mining Ore grades and mineral composition will vary depending This is the most common form of copper ore production. It on the type of mineralisation. Mined ores generally is generally appropriate for near-surface (<100 m), lower contain 0.5%–3% Cu. The first phase in processing the grade steeply dipping or massive ore bodies such as ore is concentration which increases the copper content porphyry copper, copper skarn, SEDEX and most epithermal to 25%–35%. This is typically carried out at the mine site deposits all of which are generally amenable to bulk and involves crushing and grinding, followed by chemical extraction. and/or physical processing and separation stages. Once the copper has been concentrated it can be converted into The ore is extracted by digging or blasting with explosives. pure copper metal using two techniques: It is then loaded onto trucks or conveyors and hauled to a stockpile prior to further processing. The open pit copper 1. Pyrometallurgical processes, including smelting and mine at Bingham Canyon, Utah, USA, is one of the largest electrolytic refining. man-made excavations in the world. It is over 800 m deep and four kilometres wide. It has been in operation over 100 2. Hydrometallurgical processes, including leaching, years, mining chalcopyrite with minor bornite. Bingham solvent extraction and electro-winning (SX-EW). Canyon has cumulatively produced more copper than any other mine in history, approximately 15 million tonnes. The two processes run well in parallel because during smelting pyrometallurgy produces sulphur dioxide Underground mining gas, which can be converted into sulphuric acid and Before the 1900s, copper was produced almost exclusively hydrometallurgy consumes large quantities of sulphuric from underground mines. Today, underground production is acid for leaching. less common due to the higher costs and safety issues. Currently, hydrometallurgy is primarily used only for Underground mining is suitable to extract higher grade, oxide ores. However, research into commercially feasible small or deep ore bodies. Techniques used include block extraction of copper from primary sulphides which caving (for large, uniform deposits), room and pillar can compete against smelting techniques is ongoing. (typically for flat, <30° dipping deposits), and a variety Hydrometallurgical processes have many advantages over of stoping methods (for narrow or steeply dipping veins). pyrometallurgical processes including: The Lubin mine, in the Legnica-Glogow Copper district of Poland, uses the room and pillar method of mining and • lower grade ore can be processed; currently has about 20 km2 of tunnels. • higher energy efficiency because lower temperatures are required, (although large amounts of electricity are In-situ leaching required in the electrowinning phase); A system of injection and recovery wells completed from the surface or from underground workings can be used • lower environmental impact because waste streams are to extract copper from relatively deep, low-grade ore liquid and more easily contained and neutralised than, bodies with minimal surface disturbance. The process for example, the sulphur dioxide gas which is emitted requires the deposit to be permeable and the surrounding during smelting; rock impervious41. A weak sulphuric acid leach solution • lower capital and operational costs make is pumped down injection wells and into the ore body. hydrometallurgy more economical for smaller scale Copper is dissolved into the solution as the leachate flows operations. Copper 41Impervious: incapable of being penetrated by gas or liquid. 7 www.mineralsuk.com BGS © NERC © BGS s l es - plate - sheet - foi - tubes - rods - bar Billet Cak Ingots CTURING MANU- FA c g _

Cu Cathode refinin + _

Cu Electrolyti Anode Cathode 2+ + Cu Electrowinning g g in rt r ve astin Ro Smelting Anode coppe Con LLURGICAL PROCESSES TA S 2+ ROME g lvent Cu PY te Sla So extraction mat urnace Copper F g ning aterin ke Filtering Thic Dew LLURGICAL PROCESSE TA PROCESSING t hing Va

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8 www.mineralsuk.com Suitable ore beneficiation methods are chosen and often Roasting adapted to suit the specific mineralogical characteristics Roasting converts the copper concentrates to oxides, and geographic location of the ore body. Important factors removing most of the sulphur as sulphur dioxide gas, range from the composition and texture of the ore and which can be captured and converted to sulphuric acid

gangue minerals present, to the availability of labour, (H2SO4). Other impurities, such as antimony, arsenic, and water and electricity. lead are also driven off. The concentrate is mixed with a siliceous flux42 and heated to about 650°C. Concentration Crushing and grinding Smelting The ore is fed into a primary crusher, followed by one The dry, hot roasted ore concentrate together with siliceous or more stages of secondary crushing. At each stage flux is charged into the smelter, which is maintained at vibrating screens allow material with the desired 1000–1500°C to melt the charge. Impurities are removed dimensions to pass on to the next part of the processing from the molten roasted concentrate by oxidation, leading circuit. Following crushing, the ore is mixed with water to to the segregation of a slag43 which is skimmed off and create a slurry. This is fed into a series of grinders until a discarded. Matte is the molten mixture under the slag, powder of the required grain size is produced. comprising copper and iron sulphides (35–68% Cu), which remain to be converted to pure metal. Froth flotation Froth flotation is a selective process for separating minerals Converting using water, various chemicals and compressed air. Air is blown through the molten matte to oxidise the iron and copper sulphides. This produces more sulphur dioxide, Following grinding, additional water is added to the which can be captured to make acid. A silica and lime powdered ore to produce a suspension. Air is blown flux is added which combines with the iron to form slag, upwards through the tanks. Chemicals are added, making leaving blister copper (97–99% Cu). certain minerals water repellent and causing air bubbles to stick to their surfaces. Consequently, these minerals Fire refining collect in a froth at the surface and are removed. The Blister copper is mixed with flux and enters the anode resulting concentrate is dewatered in thickeners and filters furnace, which is maintained at 1100°C. Air is blown and contains approximately 25–35% Cu, 25% S and 25% through the molten mixture to oxidise the copper and any Fe, with varying quantities of other impurities. remaining impurities. The impurities are removed as slag. The remaining copper oxide is then subjected to a reducing Leaching atmosphere to form purer copper, which is cast into Leaching is another method that may be used to anodes (99.5% Cu). This can now be used in some alloys concentrate the copper ore which can be employed either or castings but for the majority of applications, further before or after the crushing stage. This process is covered purification by electrolytic refining is necessary. in more detail under ‘Hydrometallurgical processes’. Electrolytic refining Pyrometallurgical processes The anodes cast during the fire refining stage are The copper concentrate is fed into a smelting furnace to immersed in a sulphuric acid bath in an electrolytic cell. further separate the copper from impurities. Recycled The anode44 dissolves and copper ions move through scrap copper may also enter the process. Four stages are the solution to the cathode where they are deposited involved: roasting, smelting, converting and fire refining. on ‘starter sheets’ of stainless steel or pure copper foil Some smelters combine some of these into a continuous (Figure 4). The impurities precipitate out and collect at process. Matte copper (35–68% Cu) is first produced, the bottom of the bath as sludge which can be recycled followed by blister copper (97–99% Cu). Blister copper to extract other metals such as gold, silver and platinum. can be further purified to anode copper (99.5% Cu) by fire The cathodes are removed after one to two weeks, with refining or cathode copper by electrolytic refining 50–150 kg copper deposited on each side of the original (99.95–99.96% Cu). starter sheet.

42Flux: material added to a furnace to remove impurities, lower the melting temperature, and make the slag more liquid.

43 Copper Slag: waste material, which floats to the top during a smelting operation. 44Anode: the positive electrode in an electrochemical cell. 9 www.mineralsuk.com methods of extracting copper from sulphide ores using leaching.

Solvent extraction (SX) The solution recovered from leaching is mixed with a chemical called an extractant, which selectively removes the copper from the original acidic solution leaving behind most of the impurities. A fresh acidic solution is used to strip the copper from the extractant. The resulting, highly concentrated copper solution is called a pregnant liquor solution (PLS) which is transferred to the final stage of electrowinning.

Electrowinning (EW) BGS © NERC The copper-rich solution is filtered, heated, then Figure 4 Copper cathodes. passed through a series of electrolytic cells. A much higher voltage is applied to the cells (3V) compared to electrolytic refining (0.2V), because the copper has to first Hydrometallurgical processes be reduced from copper sulphate in solution to copper Hydrometallurgical processing involves chemical or biological metal. The copper precipitates out onto stainless steel leaching of copper from the ore using dilute sulphuric acid. starter sheets to form high-purity cathodes (99.99% Cu) The weak solution is concentrated using solvent extraction and the acid is recycled. techniques (SX) and the copper is precipitated out by electrowinning (EW). In some circumstances, copper is precipitated out of the leached weak solution, before the Type Suitable for Preparation / Timescale to concentration stage, by pouring it over scrap iron to form Method extract ~70% Cu ‘cement copper’. Here the copper precipitates out onto the Dump Large No preparation Months to years iron and has to be scraped/raked off daily. This is only seventy volumes of to eighty percent pure and must then be smelted and refined. low-grade ore and waste Leaching Heap Low-grade Crushed and Days to months Copper oxide ore, low-grade copper sulphide ore or mine ores ground waste (tailings) are placed in heaps or vats (Table 4). Vat Relatively Crushed/ground Hours or days Weak sulphuric acid is trickled through the heap to low volumes, oxides agitated dissolve the copper minerals. Chemicals such as ferric generally in percolating chlorides can be added to help enhance dissolution of higher grade tanks copper sulphides. Particular strains of bacteria can be ore injected into the heap to accelerate the process, in a technique known as bio-leaching. Increasing pressure and Table 4 Processing and timescales for different leaching temperature in vat leaching can also facilitate dissolution. methods for copper oxide ores. Leaching produces a solution with a concentration of thirty to seventy percent copper which is recovered from drainage tunnels and ponds. Copper manufacture The copper cathodes produced from electrolytic refining The highest and fastest yields of copper can be extracted and electrowinning are shipped to mills and foundries from oxide ores, or those which do not contain iron. Yields where they are cast into wire rod (for wires), billets (to may reach 50% in a year and 90% in five years using the make tubes, rods and bars stock), cakes (to make plate, heap leach technique. Yield times can be as short as days sheets and foil) or ingots (for alloying or casting). These or months for vat leaching. copper and copper-alloyed products are then shipped for final manufacturing, or distribution, to meet consumers Sulphide ores generally take much longer to leach and needs. Scrap (including excess material discarded during produce a much lower yield (10–15% per year is typical manufacturing and copper-bearing products sent for in the early stages). Research is underway to find faster disposal) can be recycled back into the system. Copper

10 www.mineralsuk.com most important and widely used copper compound. Other Specification and uses important copper compounds include copper acetates, Specification cupric oxide, chloride and nitrate, cuprous chloride, copper cyanide, copper naphthenate and copper soaps. Copper is used and traded in a wide variety of forms, the most important of which are discussed below. Uses The ability to conduct electricity and heat are two of the most Copper matte a mixture of copper and iron sulphides in important properties of copper, since about a quarter of all the form of black granules or a consolidated mass. The copper produced is used in electrical applications (Figure 5). majority of matte never enters the market and is refined to a purer form. Copper’s excellent resistance to corrosion and long life span is illustrated by its extensive use in architecture, particularly Cement copper a fine black powder containing copper roofing, where it can survive for more than a hundred years. metal, copper oxides and insoluble impurities precipitated When alloyed with other metals it acquires additional by adding iron to a copper leachate solution or by pouring properties including increased hardness, tensile strength and the solution over scrap iron. improved corrosion resistance. Brass and bronze are two of the most important alloys of copper. Its malleability and ease Black copper an impure form of copper produced by of use in machines during the fabrication process allows smelting oxidised copper ores or impure scrap. Copper for a high production rate of accurate copper shapes for a content is typically in the range of 60–85%. relatively lower cost than that of its substitutes. As a result of these and other important properties discussed below, Blister copper an impure form of copper produced by copper has become a major industrial metal, ranking third blowing air through molten copper matte. The copper after iron and aluminium in terms of quantity consumed. content is generally around 98%.

Copper anodes are slabs produced from further Electrical refining. Hot air is blown through the copper at a higher Copper’s largest use is in electrical products. Copper is the temperature than for blister copper. It is then subjected best electrical conductor after silver and is widely used in to a reducing atmosphere. The cast slabs are used in the production of energy-efficient power circuits. Electron electrolytic refining. tubes used in televisions and computer monitors, audio and video amplification and in microwave ovens depend on Refined copper is metal containing at least 97.5% by copper for their internal components. Copper is extensively weight copper. Refined copper is fabricated to produce used in computers where cables, connectors and circuit finished products of various shapes according to intended end-use. These include bar, rod, tube, sheet, plate, foil, Consumer and strip, castings, and powder. general products

Industrial Copper alloys are mixtures of metals in which copper is equipment the dominant metal by weight. The precise combination Construction of elements to form an alloy is usually designed to take advantage of and enhance certain characteristics for Transportation a specific purpose. For example, copper can be mixed equipment with tin to form bronze which has superior hardness and strength than copper alone. There are over 370 commercial types of copper alloys in use today. These can take the form of cast45 or wrought46 alloys. Electrical products

Copper compounds various copper-bearing compounds Figure 5 Consumption of copper by end-use sector. are used in commercial applications. Copper sulphate Derived from: International Copper Study Group (ICSG)

(CuSO4.5H2O), a characteristically bright blue salt, is the and World Bureau of Metal Statistics (WBMS).

45Cast: metal shaped in casting moulds when molten.

Copper Wrought: metal cut, shaped or worked when solid.

11 www.mineralsuk.com boards all rely on copper. Copper is increasingly being World resources and production used in computer chips in place of aluminium, resulting in

faster operating speeds. Copper wire is extensively used World resources in telecommunications and is essential for high-speed According to USGS world identified resources of copper communication between computers. metal are estimated at about 1.6 billion tonnes, not including about an additional 700 million tonnes in deep-sea Construction nodules. Current world reserves are estimated at 467 000 Copper is used in many forms in buildings including wire, tonnes, nearly one third of which are found in Chile (Table 5). plumbing pipes and fittings, electrical outlets, switches and locks. Construction of an average modern house requires at Reserves least 200 kg of copper metal. Copper roofing is highly rated Country Percent share for its corrosion resistance and architectural characteristics. (‘000 tonnes) Chile 140 000 30.0 Consumer and general products United States 35 000 7.5 Copper is extensively used in household products. Most Indonesia 35 000 7.5 Peru 30 000 6.4 silver-plated cutlery has a copper-zinc-nickel alloy base. Poland 30 000 6.4 Copper is used in many other domestic applications including Mexico 27 000 5.8 cooking pans, lighting, clocks and for decorative purposes. China 26 000 5.6 Australia 24 000 5.1 Transportation Russia 20 000 4.3 Copper is commonly used for radiators, brakes and wiring in Zambia 19 000 4.1 motor vehicles, with a modern car containing up to 28 kg of Kazakhstan 14 000 3.0 copper. Improvements in electronics and addition of powered Canada 7 000 1.5 accessories have led to increased use of copper in modern Rest of the world 60 000 12.8 cars. Copper-nickel alloys are biotoxic and help reduce the growth of organisms on the hulls of ships and boats. Table 5 World copper metal reserves 2005. Source: USGS.

s 12

onne 10 t

on on 8 illi M 6

40 45 50 55 60 65 70 75 80 85 90 95 00 05 19 19 19 19 19 19 19 19 19 19 19 19 20 20 Year Europe and Russia Africa North and Central America South America Asia Australasia

World mined production World smelted production World refined production (no data pre- 1976)

Figure 6 World production of mined, smelted and refined copper 1940 – 2005. Pie charts show percentage mined in each region. Copper

12 www.mineralsuk.com World production considered as waste to be extracted using chemical and Copper is produced in around fifty countries, six of which bio-leaching techniques. However, in many cases the leach currently mine over 500 000 tonnes of copper each cycle may be measured in years, resulting in a considerable annually. The total production from these six countries lag time in copper metal production by these methods. amounts to 80% of world mine production. Total world production in 2005 was 15 million tonnes During the last 65 years global mined production of copper (Table 6). Chile is the largest copper producing country has increased at an average rate of 2.6% per year (Figure (Figure 7). In 2005 Chile produced 5.3 million tonnes 6). In the last 20 years, copper production has almost of copper, 35% of world production. The two largest doubled from 8.4 million tonnes in 1985 to 15 million producing mines in 2005 were La Escondida and tonnes in 2005. This sustained rise in copper production Chuquicamata in Chile (Table 7). can be attributed to the steady rise in copper demand from growing economies around the world. Total world production of smelter copper was 11.9 milion tonnes in 2005 (Table 8 and Figure 8). There are over 100 The proportion of copper mined in South America has smelters in operation in more than 30 countries, with Asia increased from about one quarter to nearly one half of contributing 44% of the world total production in 2005. total world production (Figure 7). This is largely due to an increase in production from Chile, from 16% of world Total % of production in 1985, up to 35% in 2005. A more stable (tonnes) world political climate has created favourable conditions for Asia 2 839 246 19 mining companies to tap Chile’s vast copper resources. In North and Central America production has declined and N & C America 2 163 854 14 the contribution from Asia has been increasing. Europe 1 549 157 10 S America 6 650 643 44 During the last 10–15 years mine production has become Africa 684 538 5 decoupled from total smelter production, whereas prior Australasia 1 122 978 7 to 1990 the two correlated very well. This divergence 15 010 416 can be explained by increasing use of hydrometallurgical extraction techniques which compete with smelter production. Table 6 2005 mine production of copper (Cu content).

Rising demand for copper means that many mines are USA now operating at almost full capacity (about 90% capacity in 2005 according to the International Copper Study Indonesia Group ICSG). Smelting and refining are also reaching a bottleneck. This, coupled with limited expansion potential Chile Peru and diminishing ore reserves of existing mines, means

that production is likely to level off unless the currently Australia high copper prices are reinvested into exploration and future production infrastructure. Mined copper production China is vulnerable to disruptions in supply caused by problems such as strikes, natural disasters and concerns over Russia

supplies of natural gas and water. Water is of particular Canada

relevance in Chile, where mines high in the Atacama Other Poland countries Desert compete for water with growing cities. Zambia

Improved mining and extraction techniques now allow Figure 7 2005 mine production of copper (Cu content) copper from lower grade ores that were previously Source: BGS World Mineral Production 2001–2005. Copper

13 www.mineralsuk.com Ranking Mine Country Main owner Production 2005 % of world 1 La Escondida Chile BHP Billiton 1 157 400 7.7 Coldeco Norte 2 Chile Coldeco 964 900 6.4 (Chuquicamata) 3 Grasberg Indonesia Freeport McMoran 662 200 4.4 4 El Teniente Chile Coldeco 437 400 2.9 5 Collahuasi Chile Anglo American 427 100 2.8 6 Morenci USA Phelps Dodge 400 000 2.7 7 Antamina Peru BHP Billiton /Xstrata 364 700 2.4 8 Los Pelambres Chile Antofagasta 322 800 2.1 9 Batu Hijau Indonesia Newmont 270 300 1.8 10 Andina Chile Coldeco 248 100 1.7

Table 7 Top 10 copper mines, based on 2005 mine production (Cu content).

Total world refined copper production was 16.6 million Chile China tonnes in 2005, from over 40 countries (Figure 9). In 2005 38% of refined copper was produced in Asia (Table 9).

Japan The majority of mines shown in Table 7 are open pit, although Grasberg in Indonesia has both open pit and underground operations (Figure 10). Production from Grasberg’s Deep Ore Zone (DOZ) is by a block cave operation Russia which is one of the world’s largest underground mines. Nineteen percent of mill throughput per day is from the DOZ. Other Poland countries USA

Canada Total (tonnes) % of world Korea, Kazakhstan Asia 5 304 000 31 Australia Republic of N & C America 1 305 000 8 Europe 2 384 000 14 Figure 8 2005 smelter production of copper. S America 2 079 000 12 Source: BGS World Mineral Production 2001–2005. Africa 382 000 2 Australasia 412 000 2 Chile China 11 866 000

Table 8 2005 smelter production of copper. Japan

Total (tonnes) % of world USA Asia 6 309 000 38 Other N & C America 2 149 000 13 countries Russia Europe 3 549 000 21 S America 3 549 000 21 Germany Peru Poland Africa 557 000 3 Korea, Australasia 471 000 3 Canada Republic of 16 584 000 100 Figure 9 2005 refined production of copper. Table 9 2005 refined production of copper.

Copper Source: BGS World Mineral Production 2001–2005.

14 www.mineralsuk.com

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uq Co An El La Es La Ch Los Pe Los 5 i 200 s nc re ) trie es Mo nn 9 coun to 99 9 9 05 nd 9 99 99 20 999 ing rs 9 9 9 s 4 sa 99 - - + 39 99

ne 99 - - - 9 9 0 ou elte - - mi 0 0 oduc 000 000 9 29 39 50 th 999

- - - - 00 00 2005 copper producing countries, top 10 mines and 2002 copper smelters. Source: ESRI ArcWorld Supplement (countries 2005 map), USGS (smelter data 2002), copper smelters. Source: ESRI ArcWorld 2005 copper producing countries, top 10 mines and 2002 10 19 9 000 00 00 y, 0 0 0 0 0 0 ) p - - - 0 0 it er sm er pr To 0 20 30 40 0 1 10 10 40 1 5 es ac gend nn ap Le Copp (c Copp (to Copper Figure 10 Mineral Statistics (production data 2005), other derived from company annual reports (top 10 mines 2005). British Geological Survey World

15 www.mineralsuk.com World trade 2005 and Chilean imports to China may increase further following the signing of a Free Trade Agreement. Peru is also a significant trade partner with China accounting for Most international copper trading takes place on three 16% of Chinese copper concentrate imports. Chile, which major metals exchanges: produces over a third of all copper globally, dominates • London Metal Exchange (LME) — copper is traded in the export market for both copper concentrate and refined dollars in 25 tonne lots; copper (Figure 11 and 12). Chile has recently reviewed • New York Commodities Exchange (COMEX) — trading is trade links with India through the signing of a Partial based on 25 000 pounds of copper quoted in dollar cents; Access Agreement strengthening trade links with central • Shanghai Futures Exchange (SHFE) — five tonne lots of Asia. In an attempt to improve security of supply and copper are quoted in reminibi. access to raw materials, China has sought partnerships with major copper-producing countries and companies. Stockpiles of the metals are held in exchange warehouses worldwide. The levels of the stockpile reflect the supply An agreement between China’s largest metals trading and demand characteristics of the physical market. company, Minmetals, and the world’s largest copper Copper traders use copper futures and options to manage producer, Chile’s Corporación Nacional del Cobre de Chile future price risk, and copper contracts may also be used as (Codelco), aims to ensure a long-term stable copper supply investment vehicles. The most important copper products to China. The deal provides China with 55 000 tonnes of in international trade in 2005 were refined copper (57%), refined copper each year for over 15 years in exchange concentrate (36%) and blister copper (7%). In addition for help from China in developing projects in Chile. The to refined copper, trade in semi-fabricated products and European Union is heavily dependent on the refining and copper alloys has grown rapidly in recent years. smelting of concentrates imported from countries such as Australia, Chile and Indonesia and recycling of production During the last decade there has been a major relocation scrap or end-of-life products. of global manufacturing capacity towards the emerging economies of central Asia, in particular, China. The impact Prices of these changes is obvious in the natural resources markets where direct copper usage is shifting from The price paid for copper on the metal exchanges primarily developed countries to newly industrialising nations. reflects global balances of copper supply and demand, This has had a significant influence on copper trade flows but may be significantly affected by speculative activity, worldwide. currency exchange rates and market news.

Chinese imports of copper concentrates have increased Copper demand and price typically reflect global economic rapidly since 2002, driven by extensive growth in smelting cycles and, as a result, the copper price has historically capacity. Japan and China are the two largest importers of experienced major fluctuations (Figure 13). There were copper concentrate worldwide (Figure 11). Chile accounted times in the 1990s when the copper price approached $3000 for 40% of copper concentrate supplied to China in tonne. However, for a five-year period up to the end of 2003

(a) (b) Portugal Other United States Other Canada Brazil Mongolia Japan Argentina Finland Papua New Philippines Guinea Chile

Canada Spain

Australia Germany

Peru South Korea China Indonesia Figure 11 Trade in unrefined copper in 2005 (a) Exports (b) Imports. Source: World Metal Statistics. Copper

16 www.mineralsuk.com (a) (b) Other Other China

Chile Turkey

Japan Thailand Indonesia Malaysia USA Poland South Korea Canada Russia France Italy Australia Peru Zambia Kazakhstan Germany Taiwan

Figure 12 Trade in refined copper in 2005 (a) Exports (b) Imports. Source: World Metal Statistics.

copper prices were relatively stable trading between $1400 price of copper has increased, with spectacular gains since and $2000 tonne. Towards the end of 2003 and early 2004 2003 (Figure 13). prices began to increase, reaching $4500 tonne by the end of 2005. Many analysts at the time suggested this The copper market was exceptionally strong during 2006 elevated copper price was not sustainable. However, the with copper prices averaging $6700 tonne over the whole price continued to escalate in 2006. Although the price of year, an 83% increase over 2005 (Figure 15). During the copper currently appears very high in terms of US$/tonne, first five months of 2006, copper prices continued their in real47 terms the current price is not quite as exceptional upward trend and in May the LME spot price reached a as it seems in nominal48 terms. Real copper prices followed record-high of $8780 tonne, with an average price for the a general downward trend up to 2002 whilst the nominal month of $8044 tonne.

$7 000

$6 000

$5 000

$4 000 nne to

$/ $3 000 US $2 000

$1 000

$0 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 Nominal Real 2000 price price

Figure 13 Historical spot price for copper 1976–2006. Derived from: Metal Bulletin. Real price adjusted for changes in the value of money compared to 2000.

47Real price: is adjusted for changes in the value of money. 48Nominal price: ignores changes in inflation and other factors. Copper

17 www.mineralsuk.com

20 /

/12

US employment 6 data announced

Strike at Xstrata's Altonorte copper smelter 0

20 /

Hindalco suspend operations at one smetler

6 0

Bloomsbury Mineral refined copper market 2007 Economics predicts will run a surplus in

4 1

Freeport-McMoran of Phelps Dodge announces takeover

20 /

LME copper inventories rising 0

LME stockpiles grew by 40% since mid- October /1 4 2

China sells copper at higher prices than estimated 6 Speculation US 0 demand is slowin

enters third week Escondida strike 20

reached at Escondida / Provisional settlement

/08

Mexico's Cananea mine 2 Strike ends at 2

August Workers vote to strike at Escondida in strike starts Escondida in Mumbai Train bombings

6 Earthquakes reported in Chile 0

Escondida Strike threat at 20

1 1

Chinese copper Rumours of auction

Interest rate rises in many countries 0

ICSG report indicates and February reduced a copper surplus in January global consumption

20 /

Chinese Central credit Bank tightens

are likely to / KGMB suggests copper shortages continue

Upcoming Chinese copper auction 0 3

interest rates 6 China raises

state La Caridad Mexican Government mine strike is illegal

20 / /05

they cannot guarantee April contracts Grupo Mexico report supplies beyond

Copper inventories at drop to four weeks 9 three main exchanges global supply 0

and lowering LME inventories 0 Continued strikes in Mexico

20 /

/04

8 1

Grupo Mexico claim it will close its San Martin mine

BHP Billiton suggest to end 2008 0 concentrate shortage there will be a copper

Freeport McMoRan 6 announces Grasberg is back in production

Global copper 0 inventories reach consumption 2.5 days global Commission increase forecast for 2006

Chilean Copper average price

20 /

Lomas Bayas off /0 Strike at mine called 7 0

owned by Grupo Strikes at mines Mexico

foresees a deficit in 2006 Analysts report copper supply

fund selling 20 Investment

4 1

Chinese New Year

4 2

strike at Chile's Contract workers Codelco mines Investment fund buying

6 0

Key factors influencing copper prices in 2006. Derived from: Metal Bulletin, Copper Spot LME Daily Official. BGS © NERC. Key factors influencing copper prices in 2006. Derived 0

8000 /01 9000 6000 5000 7000 4000 3

1000 0

e tonn US$/ Copper Figure 14

18 www.mineralsuk.com The deficit in the availability of refined copper experienced growth and its automotive and construction sectors are during the previous three years persisted into 2006 rapidly developing. The copper consumption picture during resulting in tight supply and critically low levels of stocks 2006 was complex, with conflicting reports regarding in exchange warehouses, amounting to less than three Chinese consumption. In 2006, world copper consumption days global consumption at times. The supply-demand increased by only four percent over 2005 to 17.4 million imbalance ensured prices reacted strongly to market tonnes, a much smaller increase than in previous years. developments resulting in considerable volatility and Estimates suggest Chinese copper consumption declined price spikes. Higher metal prices resulted in increased by around one percent despite continued strong economic speculative demand for copper as an investment. Global growth, although unreported State Reserve Bureau copper mine production in 2006 was lower than expected as a sales cloud China’s true consumption figures. result of production problems and labour disputes resulting in strikes in key copper-producing countries. Grupo Mexico Chinese copper imports decreased in 2006 in response experienced considerable losses as a result of strikes at a to higher prices and increased domestic availability from number of its operations. Production at Chile’s Escondida domestic cathode production, state reserves and greater mine was interrupted for most of July by labour disputes scrap recycling. According to reports by the International causing loss of an estimated 45 000 tonnes of contained Copper Study Group (ICSG), during the first 9 months of copper. At total of around 500 000 tonnes of production, 2006 there was a global copper surplus of more than 80 or three percent of global production, is estimated to have 000 tonnes compared with a production deficit of more been lost as a result of disruptions associated with labour than 300 000 tonnes during the same period in 2005. disputes and other operational problems during 2006. Developments in China and the USA, the world’s largest By the end of 2006, copper prices had fallen considerably copper consumers, are likely to have the greatest impact on from the record highs in May of that year. This reflected future global copper consumption. Copper demand in China moderation in demand, recovery of global mine output is predicted to continue growing, driven by further growth in from disruptions earlier in the year and growing exchange the construction sector as well as a requirement to replenish inventories. In addition, escalating oil prices and an abrupt Chinese inventories which were depleted during 2006. decrease in United States house building signalled possible global economic slowdown resulting in decreased demand Rising copper prices in recent years have led to investment in for industrial materials. Exchange inventories reached a low new production capacity, expansions at key operations and of 153 000 tonnes in July 2006 rising to over 210 000 tonnes previously uneconomic projects becoming viable. However, in November. At the end of 2006, however, prices remained the large projects in particular have considerable lag times 45% higher than at the end of the previous year. and some have encountered problems. Global copper mine production is forecast to grow by six percent in 2007. The underlying reason for rising metal prices during the Phelps Dodge commissioned their Cerro Verde expansion last three years has been growing demand from emerging in Peru in early 2007, adding around 145 000 tonnes a year economies, primarily China. Copper consumption has been to production and a number of smaller operations are also driven by rapid expansion of the Chinese electronics and due to come online. Record copper prices have also spurred construction sectors both of which are heavily dependent consolidation within the sector. Notable is Freeport- on copper. China accounts for around 25% of world McMoRan Copper & Gold Inc’s takeover of Phelps Dodge to copper consumption. India has also shown strong signs of create the world’s largest publicly traded copper producer. Copper

19 www.mineralsuk.com Alternative technology • home scrap or run-around scrap - is the punching, borings, turnings and cuttings generated in foundries Secondary production: recycling and mills which are taken back to the casting shop, where it is re-melted and cast into cakes. Secondary production, derived from the recycling of copper scrap, accounts for around two thirds of total • prompt scrap, industrial and return scrap — are the copper production (Figure 15). Copper and its alloys stampings, cuttings and turnings produced when the can be continuously recycled without diminishing their semi-fabricated products are converted into parts in useful properties. Producing copper from recycling takes metal workings shops. It is usually returned to the mill approximately one sixth of the energy required to produce that supplied it. copper from ore (because the oxidation and reducing stages are not necessary). As a result, a large proportion Old scrap (~80%) of all the copper that has ever been mined is still in This is all post-consumer scrap derived from worn out use today. or obsolete copper products. It is harder to collect and separate for recycling than new scrap, as it is often mixed The way in which copper scrap is recycled depends on with other materials in a single appliance. This scrap is its purity. High purity copper or specific alloy mixes are usually sold to a merchant or dealer, who, in turn, sells it to collected and segregated and can simply be re-melted in a a mill or other processor for sorting. Old scrap comprises: smelter and recast for use in subsequent fabrication. With alloys, minor adjustments can be made to the composition • end-of-life vehicles (ELV) — the copper is recovered while it is molten, in order to bring the resulting mixture up and recycled from radiators, engine parts and electronic to specification. Less pure or mixed scrap can be smelted components. and directly recast for use in non-electrical applications where purity is not so critical, such as plumbing and • construction & demolition (C&D) — includes wiring, roofing. Alternatively, scrap can be mixed with pure copper roofing and plumbing materials. to ‘dilute’ the impurities, or, if necessary, cast into anodes • waste from electrical and electronic equipment (WEEE) and electrolytically refined, as in the final stages of primary — mainly consists of circuit boards and wiring, which copper processing. If the scrap includes certain specific can be difficult and expensive to separate as they materials, for example tinned or lead-soldered copper, may contain hazardous materials, such as mercury or it may be more economic to take advantage of these batteries. contaminants, rather than trying to remove them. Certain alloys which contain those metals, such as gunmetal and bronze, can use this scrap as smelter feedstock. Substitutes Copper in electrical applications It is important that the waste streams of copper scrap Silver is the best electrical conductor known to man for recycling are segregated to avoid unnecessary and copper is the second, but silver is too expensive to contamination of the copper with impurities which be economically used in electrical wires. Other cheaper will involve extra processing to remove. Scrap can be alternatives include aluminium. However, non-copper wires classified in several ways, but it can broadly sub-divided can ‘creep’ causing connections to loosen and therefore into two categories, new scrap and old scrap. require checking periodically. Also anti-oxide paste must be applied where the wires are joined and connected, as New scrap anodic corrosion can cause the aluminium to disintegrate. This includes all scrap from processing to manufacturing, Aluminium oxide does not conduct, although copper oxide before it enters the consumer market. New scrap does. A combination of the two metals has been used comprises: in bimetallic copper-clad aluminium (CCA) wire, which is an aluminium core covered with copper cladding. It costs • process scrap — includes processing residues, and weighs less, and handles and installs more easily slag, fines and drosses49. It is usually 100% reused than solid copper wire. In certain telecommunications immediately within the plant. applications optical fibre can replace copper wire. Copper 49Drosses: solid metal processing waste. 20 www.mineralsuk.com BGS © NERC © BGS

fining y copper k copper re ing rt r an efining ve fo -99% Cu olytic e r Smelting application 99.5% Cu 99.99% Cu 60-85% Cu 97 Con Fir w els Electr produce blac produce blister copper produce anode copper Suitable produce cathode copper 0-40% copper 1 To To To To p ity lev ra iciently lo ff

ed sc e su

ap If impur ar ity/mix or ys e the ation of scr ity is not so w pur

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or alloys, purity is r F

fo r. ys

eatment: Smelting Re-casting Allo e-tr Suitable Pr specifications suit its special applications whi tested and adjusted as necessary ready for fabrication/manufacturing re-melt the coppe To

re-form the copper into rods, billet, ca ical To or high ity copper applications 99.99% copper quality electr Suitable f High pur The copper recycling process. Copper Figure 15

21 www.mineralsuk.com Water pipe and plumbing fixtures copper-lead alloy) in manufacturing and repair shops. The Aluminium and plastics are the two most common lead-tin solder used in brass radiators can also ‘creep’ and substitutes for copper for this application. There is an cause leaks. aluminium plastic composite water piping system, which is made of aluminium tube, laminated inside and out with Miscellaneous plastic, to create piping that is lightweight, flexible, strong, Steel now substitutes for copper used for artillery shell corrosion-resistant and that can be easily bent or formed casings because it is cheaper. Aluminium is often used in by hand. Plastics include CPVC, PVC and PEX which are cooling fins and refrigerator tubing. cheaper, have reduced noise, are more energy efficient, have less condensation than copper, no corrosion or scale Research and development build up, no pin hole leaks and are chlorine resistant. They Research into improving the efficiency and cost are also easier to install and modify at a later stage. effectiveness of extracting and processing copper is ongoing. Heat exchangers Copper is commonly used for heat exchangers filled with A variety of chemical and biological techniques to leach water or ethylene glycol with water. Alternative materials copper, particularly from sulphide ores, is being developed, include steel, titanium, aluminium and plastic, each of with many pilot plants in operation around the world. which lend themselves to particular applications: Some of these processes have already entered commercial use, such as the BIOCOPTM process used by BHP Billiton • Stainless steel heat exchangers can operate at higher in Chile, HydrocopperR developed by Outokumpu and temperatures and are more rugged than copper ones. commissioned in Erdenet, Mongolia. They are ideal for heating or cooling corrosive fluids in chemical, pharmaceutical, and refining processes. These techniques include leaching under elevated pressure and/or under raised or controlled temperatures. • Titanium units can also tolerate high temperatures Others involve addition of catalysts (such as silver ions), and high pressures, with superior corrosion resistance. chemicals (such as chlorides), or bacteria cultivated They are also 5–10 times lighter than their steel under particular conditions (called biohydrometallurgy counterparts, although they are much more expensive. or bio-leaching). Bacteria can be used to speed up They are often used in marine applications. and optimise copper yields under certain conditions. • Aluminium is mainly used in cold temperature The effectiveness of the process depends on the ore applications (to -270oC). It has good heat transfer mineralogy and how easily the optimum conditions can performance, relatively high pressure ratings and is be maintained. lighter than other metals. As hydrometallurgical technology is refined it will enable • Plastic — polyvinylidene fluoride, polypropylene, and lower grade ores which had previously been considered polyethylene construction is specifically useful for waste, to potentially yield copper in a cheaper, more highly corrosive gases, for example in the condensation efficient and environmentally friendly way than the recovery of acidic components from biological waste traditional pyrometallurgical processing route. incineration. Copper’s versatility ensures that new uses continue to Automotive radiators be explored. Expanding markets are in the construction, In the past automobile radiators were largely made electrical and marine transport industries. Health and of brass, because of its machinability, and thermal medical applications are beginning to take advantage of conductivity properties. A common substitution is now the natural antibacterial properties of copper metal. These aluminium. This is because aluminium is lighter and less include applications such as lining water containers in affected by corrosion from the coolant. In addition there countries where access to clean water is limited and use were environmental concerns about the lead (brass is a in hospitals and food preparation areas. Copper

22 www.mineralsuk.com Focus on Britain newer discoveries being re-evaluated such as Anglesey Mining’s Parys Mountain project in North Wales. Known occurrences Copper mineralisation occurs in many areas of Britain The following types of copper mineralisation have and although there is currently no copper production, been identified in the UK (Figure 17). A more detailed Britain has an important history of copper mining. There description of localities and specific deposit types of is evidence of Bronze Age copper mining in south-west copper mineralisation found in the UK is covered by the England and in North Wales. In Cornwall, copper and tin report ‘Exploration for metalliferous and related minerals were traded with the Phoenicians as early as 1500 BC. The in Britain: a guide’. Parys Mountain Mine in Anglesey, North Wales, which may have been mined during Roman times, was the world’s Porphyry deposits largest copper producer for a period in the eighteenth Disseminated copper mineralisation, locally with gold century (Figure 16). Returns for the whole of the enrichment, occurs at several localities associated with nineteenth century show Britain to be the world’s fourth Caledonian50 intrusive rocks. The best known deposit largest copper producer, accounting for nearly ten percent is Coed y Brenin, near Dolgellau in North Wales. This of total production. Extraction fell rapidly towards the end deposit contains 200 million tonnes grading 0.3% Cu, of the century and the last UK copper mine, the Wheal with trace gold. Coed y Brenin lies within the Snowdonia Jane tin-zinc-copper Mine in Cornwall, closed in 1991. National Park and proposals to mine it in the 1970s met considerable opposition. Up until 1914 a breccia pipe The decline of British copper mining was mainly the containing copper-gold mineralisation was worked at the result of falling metal prices and competition from Glasdir mine close to Coed y Brenin, with total production overseas (Chile, Australia and USA). Deposits were not of of about 75 000 tonnes at 1.5% Cu. In the south-west sufficiently high grade or abundance to remain economic. Highlands of Scotland, disseminated polymetallic After a long period of relatively low priced copper, the mineralisation of epithermal-porphyry style is found at recent upturn has resulted in some of the old mines and Lagalochan. BGS © NERC

Figure 16 Parys Mountain mine in North Wales.

50Caledonian: a period of mountain building from middle Ordovician to mid-Devonian times, resulting in deformed rock and granitic intrusions over much of Scotland. Copper

23 www.mineralsuk.com Shetland Islands

Vidlin Ness

Gairloch Volcanogenic stratabound Flowerdale Knock Volcanogenic massive sulphide Forest Porphyry Mafic intrusion-hosted Kilchrist Sediment-hosted Breccia pipe Skarn Ardsheal Tomnadashan Epigenetic in limestone

Ballachulish Garbh Vein style (old mining areas) Achadh Lagalochan Edinburgh McPhun's Cairn Meall Mhor

Glendinning Fore Burn

Cairngarroch Middleton Tyas Black Stockarton Moor Lake District N Alderley Llandudno Edge Parys Mountain Ecton Hill Cae Coch Snowdonia

Coed-y-Brenin Glasdir Central Wales

Llandeloy

Treffgarne London

Cardiff

Belstone

Higher South-west England Coombe Devon Gt Consols 0 100 200 kilometres

24 www.mineralsuk.com Red-bed deposits 10 years extensive geological studies and drilling have Triassic (250 to 210 million years) red-beds in the English been conducted at the site. According to recent reports, Midlands are locally enriched in copper. The sandstones51 Anglesey Mining are planning to develop the project, and conglomerates52 of the Sherwood Sandstone Group focusing on the near-surface part of the deposit which in the Alderley Edge area of the Cheshire Basin are has an estimated resource totalling 2.15 million tonnes at historically most productive. The ore is dominated by 0.36% Cu, 2.11% Pb, 4.13% Zn, 40 g/t Ag and 0.42 g/t Au. copper carbonates with small amounts of lead, cobalt, The only other deposit of this type known in Wales is the zinc and traces of gold (Figure 18). Barytes is commonly Cae Coch massive pyrite deposit of Orodvician (505 to 440 associated with the ore minerals. The mineralisation million years) age in Snowdonia. preferentially develops in traps created by faulting53 and the overlying rocks. The deposits, which were worked from the Besshi-type56 copper-zinc-gold mineralisation is found late 1600s to the 1920s, had an estimated grade of 2.1% in basic Lewisian57 rocks near Gairloch in north-west Cu and produced around 3200 tonnes of recovered metal. Scotland. Two laterally extensive sulphide horizons were located, one of which can be traced for over 6 km and consists mainly of iron sulphides. The other, with a length of at least 1 km, comprises a 4 m thick quartz-carbonate schist58 with pyrite, pyrrhotite, chalcopyrite and gold. The deposit was extensively drilled in the early 1980s. Reported grades were about 1% Cu, 0.5% Zn and 1 g/t Au which were not economic at that time. Stratabound sulphides enriched in Pb-Zn-Ba and locally copper are widespread in the Dalradian59 rocks of Scotland. The richest deposit is at Vidlin Ness in the Shetland Islands where drilling revealed stratabound sulphides reaching 10 m thick and grading up to 1.19% Cu and 1.27% Zn. In south-west England stratabound base-metal mineralisation occurs locally in Devonian (410 to 360

BGS © NERC million years) and Carboniferous (360 to 290 million years) sedimentary and volcanic rocks. Drilling intersected low- Figure 18 Mineralised sandstone from Alderley Edge. grade disseminated and veinlet copper mineralisation near Higher Coombe in Devon.

Volcanic massive sulphide (VMS) and SEDEX deposits Magmatic sulphide deposits Parys Mountain on Angelsey in North Wales is the most Layered mafic-ultramafic intrusions of late Caledonian significant VMS deposit known in Britain and a historically age underlie large areas in north-east Scotland and have important copper producer. The deposit was extensively been the subject of exploration for nickel-copper and PGE mined by open pit and underground methods, producing mineralisation. Exploration of the Aberdeenshire mafic- around 300 000 tonnes of copper in the late 1700s. ultramafic intrusives in the 1960s and 1970s led to the drilling of the Knock intrusion and identified a geological Mineralisation at Parys Mountain is associated with reserve of 3 million tonnes grading 0.52% Ni and 0.27% highly altered volcanic rocks and mudstones54. In 1992, Cu. Work at Arthrath, near Aberdeen, intersected weakly Anglesey Mining determined a geological resource55 of mineralised intervals of nickel-copper sulphides over an 6.5 million tonnes with an average grade of over 10% extensive area. Alba Minerals is currently prospecting the combined Zn, Cu and Pb, with Au and Ag. Over the last area and have drilled new holes to verify historical data.

51Sandstone: a sedimentary rock composed of sand-size mineral or rock grains. 52Conglomerate: a coarse-grained sedimentary rock typically containing rounded particles. 53Fault : a fracture in the Earth’s surface along which the opposite sides have moved. 54Mudstone: a fine-grained sedimentary rock composed of clay sized particles. 55Resource: a concentration of material in the Earth’s crust of economic interest. 56Besshi-type: a sub-division of VMS deposits based on metal content. 57Lewisian: highly deformed rocks in north-west Scotland. 58Schist: a medium-grade metamorphic rock containing platy and elongated minerals. 59 Copper Dalradian: a succession of Late Precambrian (4000 to 590 million years) and Cambrian (590 to 505 million years), mainly sedimentary rocks found in Scotland and Ireland.

25 www.mineralsuk.com Vein-style deposits Consumption These are associated with either granitic intrusions (south- Britain is a major consumer of copper and copper- west England), volcanic rocks (North Wales and Lake containing products. The metal is used principally in District) or sedimentary basins (Central Wales). Historically manufacturing (electronics, cars, white goods), building vein deposits have been important sources of copper in (electrical systems), chemicals (dyes, explosives, Britain, particularly those in south-west England, which preservatives) and agriculture. was the world’s main source of copper in the first half of the nineteenth century. The mineralisation in this region In 2005 the United Kingdom consumed 165 400 tonnes occurs in association with Hercynian60 granites. The main of refined copper, which equates to one percent of total copper mineralisation generally occurred above the tin- world consumption (Figure 19). Within Europe, Britain bearing parts of the system. is the eighth largest consumer of copper goods, after Poland, Spain, Belgium, France, Italy, Russia and Germany Epigenetic deposits in limestones (Germany has the largest consumption in Europe). At Ecton Hill in the Southern Pennine Orefield about 100 000 tonnes of ore containing 15% Cu were extracted British consumption rose through the 1990s to a peak of 408 in the 1800s from two pipe-like vertical orebodies and 500 tonnes in 1997 and has since declined by nearly 40%. associated veins hosted by limestone. Small but very high- grade copper deposits have also been mined in cavernous The European average consumption per capita is 6.4 kg Carboniferous limestones near Llandudno in North Wales, copper, whereas the British figure is less than half of that, at Llanymynech in the Welsh Borders and near Middleton at 2.8 kg per capita (World Bureau of Metal Statistics and Tyas in Yorkshire. United Nations Department of Economic and Social Affairs).

450 400 350 onnes)

t 300 250 housand housand

(t 200 n n

io 150 100

Consumpt 50 0 1990 1994 1998 2002 2006

Figure 19 Consumption of refined copper in the UK from 1989 to 2006. Source: World Bureau of Metal Statistics.

60Hercynian (Variscan): a period of mountain building during the Carboniferous which resulted in deformed rock and granitic intrusions over much of south-west England and western Europe. Copper

26 www.mineralsuk.com Further reading and selected references

Useful contacts for further information

London Metal Exchange www.lme.co.uk New York Metals Exchange www.nymex.com Copper Development Association www.copper.org International Wrought Copper Council www.coppercouncil.org European Copper Institute www.eurocopper.org International Copper Association www.copperinfo.com International Copper Study Group www.icsg.org Specific mining project information www.mining-technology.com British Colombia Mineral Deposit Profiles www.em.gov.bc.ca Natural Resources Canada www.nrcan-rncan.gc.ca/com United States Geological Survey www.minerals.usgs.gov World Bureau of Metal Statistics www.world-bureau.com

Selected references and further reading

AYRES, R U, AYRES, L W, and RADE I. 2002. The life cycle EVANS, A M. 1993. Ore geology and industrial minerals, of copper, its co-products and byproducts. Mining minerals an introduction (3rd edition). Blackwells Scientific and sustainable development [online]. London, England. Publication, Oxford. International institute for environmental development. Available from www.iied.org [cited February 2007]. GALLEY, A, HANNINGTON, M, and JONASSON, I. Date unknown. Volcanogenic massive sulphide deposits [online]. BARTOS, P J. 2002. SX-EW copper and the technology Ontario, Canada: Natural Resources Canada. Available cycle. Resources Policy vol 28, pp 85–94. Elsevier, from http://gsc.nrcan.gc.ca [cited 28 March 2007]. Amsterdam. KANG, H Y, and SCHOENUNG, J M. 2002. Electronic waste BRISKEY, J A. 1986. Descriptive Model of sedimentary recycling: A review of U.S. Infrastructure and technology exhalative Zn-Pb. In: COX, D P. and SINGER, D A. Mineral options. Resources, Conservation and Recycling, vol 45, Deposit Models. U.S. Geological Survey, Bulletin 1693. pp 396–400. Elsevier, Amsterdam. MOSIER, D L, SINGER, D A, and COX, D P. 1986. Grade and CLARK, M E, BATTY, J D, VAN BUUREN, C B, DEW, D W, tonnage model of sediment-hosted Cu. In: COX, D P. and and EAMON, M A. 2006. Biotechnology in mineral SINGER, D A. Mineral Deposit Models. U.S. Geological processing: technological breakthroughs creating value. Survey, Bulletin 1693. Hydrometallurgy vol 83, pp 3–9. Elsevier, Amsterdam. PANTELEYEV, A. 1996. Epithermal Au-Ag-Cu: COLMAN, T B. 1998. Minerals in Britain: Past High sulphidation. In: LEFEBURE, D V and HÕY, T. production… future potential. Copper edition. DTI Selected British Columbia mineral deposit profiles, commissioned report, British Geological Survey, Volume 2 — Metallic deposits. British Columbia Ministry Nottingham. Available from www.mineralsUK.com. of Employment and Investment, Open File 1996-13.

COLMAN, T B, and Cooper, D C. 2000. Exploration for PASCOE, W H. 1981. The history of the Cornish Copper metalliferous and related minerals in Britain: a guide, 2nd Company. Dyllansow Truram, Cornwall. edition. British Geological Survey, Nottingham. PEACEY, J, GUO, X, and ROBLES, E. Date unknown. Copper DREISINGER, D. 2006. Copper leaching from primary Hydrometallurgy — Current status, preliminary economics, sulphides: Options for biological and chemical extraction future direction and positioning versus smelting [online]. of copper. Hydrometallurgy vol 83, pp 10–20. Elsevier, Mississauga, Canada, Hatch Ltd. Available from Amsterdam. http://www.hatch.ca [cited 29 March 2007]. Copper

27 www.mineralsuk.com PORTER, L, and ROBEY, J. 2000. The copper and lead mines Tyler, P A. 2003. The Parys Mountain volcanogenic around the Manifold Valley, North Staffordshire. Landmark sulphide deposit, North Wales: a new interpretation. In: Publishing Ltd. Derbyshire. Europe’s Major Base Metal Deposits, Irish Association for Economic Geology. SPATARI, S, BERTRAM, M, FUSE, K, GRAEDEL T E, and RECHBERGER, H. 2002. The contemporary European UNEP/IEPAC 1991 Environmental aspects of selected copper cycle: waste management subsystem. Ecological non-ferrous metals ore mining, a technical guide, Technical Economics vol 42, pp 43–57. Elsevier, Amsterdam. Report Series no 5, UNEP, France.

TAYLOR, A. 2002. Copper SX/EW- any rivals in site? UNITED NATIONS, Department of economic and social [online]. Brisbane, Australia, Alta metallurgical services. affairs. Population snapshop 2005 for section Available from http://www.altamet.com.au [cited 18 http://esa.un.org/unpp/ [cited 25 February 2007]. December 2007].

TAYLOR, A. 2002. Big guns now on copper concentrate U.S. GEOLOGICAL SURVEY, 2003, Map and table of world leaching race [online]. Brisbane, Australia, Alta copper smelters: U.S. Geological Survey Open File-Report metallurgical services. Available from 03-75, [online] Reston, Virginia, U.S. Geological Survey. http://www.altamet.com.au [cited 28 March 2007]. Available from http://www-tin.er.usgs.gov/index.shtml [cited 20 February 2007]. TRICKEY, S J. 2005. Mineral economics of the global copper industry: ores, wastes and end-products. WORLD BUREAU OF METAL STATISTICS. 2007. World Unpublished MSc thesis, University of Exeter. metal statistics vol 60, no 3. Ware, Hertfordshire. Copper

28 www.mineralsuk.com